Sockets of multi connect server's client do not close on minor change from eco server to normal server and normal client

ℹ️
After I use it (https://github.com/realpython/materials/blob/master/python-sockets-tutorial/multiconn-client.py) with a small change (minor change from echo server to normal server) -

- after sending and receiving messages from the client and server, the client does not close; or
- all data.messages have been exausted, the client does not close.

https://stackoverflow.com/questions/70640602/sockets-in-python-client-not-closing-after-event-read-write-events-in-multi-conn

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Describe the bug
After minor change from echo server to normal server:

- after sending and receiving messages from the client and server, the client does not close; or
- all data.messages have been exausted, the client does not close.

To Reproduce
Provided in the stackoverflow question

Expected behavior
The client should close. Looks like it does not get into the if not recv_data code while I was checking. The program should reach the code. No major changes to the code has been made other than sending data from messages section. :

if not recv_data:
    print("closing connection", data.connid)
    sel.unregister(sock)
    sock.close()

Screenshots
Added to link:
https://stackoverflow.com/questions/70640602/sockets-in-python-client-not-closing-after-event-read-write-events-in-multi-conn

Desktop (please complete the following information):

• OS: [e.g. iOS] Win, Linux

Additional context
NA

Start with python-sockets-tutorial/multiconn-client.py and the linked Stack Overflow reproduction; compare the echo-server change with the described normal-server flow. Confirm that, after messages are exhausted, the client reaches the shown if not recv_data branch and closes. Done means the client closes reliably in both described cases.